It follows the Serious Fraud Office confirming it has begun a criminal investigation after the company’s finance director was arrested last night and released on bail.
Patisserie Holdings says Johnson is expected to provide a £10m, three-year loan on an interest-free basis.
He will also commit to a further bridging loan of up to £10m to allow the bakery chain to keep trading.
A further £15m will be raised by issuing new shares.
The company says once completed the fundraising will allow its 200+ sites to continue trading “for the foreseeable future”.
It says that it would have to enter administration without an immediate £20m cash injection.
The funding will primarily be used to pay immediate outstanding liabilities, including amounts owed to HM Revenue & Customs and trade creditors.
Patisserie Holdings also confirmed it has net debt of approximately £9.8m.
It says statements on the cash position of the company were mis-stated and subject to fraudulent activity and accounting.
The company suspended its shares on Wednesday amid an investigation in to potential fraud.